New agreement for Y-12, novel approach to solve tin-whiskers dilemma

Y-12 will sign a lead free electronics cooperative research and development agreement with Foresite Inc., of Kokomo, Indiana. Working together, this team expects to take down the scientific Goliath known as tin whiskers, which can cause catastrophic failures in electronics.

“As the first funds in CRADA in recent memory, it will create new opportunities for funded engineering development at Y-12, which falls within a discipline of increasing importance to all electronics manufacturers,” Dennis Miller of Program Integration said. “Although initial funding for the project will be relatively low, the focus of the CRADA will be on the importance of the scientific and developmental potential that’ll be created.”

Foresite’s financial commitment will fund Y-12, and later Foresite will invest significantly more relative to their position as a small business in a highly competitive market. “The investment itself indicates the value Foresite places on Y-12’s technology,” Miller added.

“At the onset of the electronics age, development of electrical devices, wires, and electrical components were joined using tin solder,” Rusty Hallman of Mission Engineering said. “Metallurgical properties of tin tend to be brittle, producing such high stresses within the grain of the metal so that small filamentous ‘whiskers’ are formed from select low energy grains. These whiskers grow long enough to contact neighboring circuits, causing short circuit failure. In high voltage circuits, plasma fires and subsequent catastrophic failure occur.”

The 1950 discovery that adding lead to tin to form an alloy (1) relieved metallic stresses and stopped the formation of whiskers, (2) revolutionized the electronics industry, and (3) provided a reliable and predictable means of manufacturing the complex electronic systems in use today.

At present, the European Union has enacted legislation known as the Reduction of Hazardous Substances, to eliminate lead and other hazardous substances from electronics. “The impact is significant. Manufacturers around the world have removed lead from solder in manufactured electronics. As a result of RoHS compliance, the tin whisker problem and other pre 1950 performance problems associated with lead free electronics have returned,” Miller said. “We’re experiencing tin whiskering, poor ductility, poor shock and vibe tolerance, poor wetting of leads in manufacturing, and other problems.”

A host of new problems now exist as a result of the higher density of smaller components in electronic systems, increased heat loads and power demands, and application of electronics into ever increasing critical applications.

Many approaches have been tried to solve RoHS related problems. Most rely on well established electronics industry solutions such as substitution of alloying agents, new solder fluxes, post heat treatments, conformal coatings, etc. However, none has effectively addressed the fundamental scientific problem of altering the basic behavior of the formed metal joint in the absences of lead.

“Y-12’s approach to the problem is novel and counterintuitive but scientifically sound,” Hallman said. The fundamental principle is that the microstructure of a material is a result of its processing parameter, and the material’s performance is a result of the microstructure. If the processing parameter to be adjusted is known, designed-in material performance can be achieved.

All materials have some kind of magnetic response, and Y-12 has demonstrated that response in soldered and plated test specimens. When solder is molten, it is susceptible to being rearranged and aligned magnetically. When cooled, the material retains this otherwise unobtainable structure. “This new processing method of solidification within a magnetic field provides a fresh path to reproducibly create structures that lead to desirable material performance for lead-free electronic components and subsystems,” Hallman said.

Currently, electronics industry researchers are following only conventional electrical engineering principles and are getting the same results that have been obtained for years with no resolution. Y‑12’s novel use of magnetic fields for our solution draws upon a broader materials science background, offering a new perspective using processing parameters — previously not considered — to obtain microstructure control previously thought to be unobtainable.

Although proving the negative that we can prevent tin whisker propagation in lead free soldered and plated electronic components remains a considerable challenge, many of the side benefits of Y-12’s patented technology, called Magnofex, offers clear solutions to issues of poor wetting, shock and vibration failures, weakened sheer, elevated melting point, etc. The near term progress in solving these problems offered by the CRADA will lend credibility to Y-12’s technology, will offer additional patent opportunities, and will offer technological advancements in reflow machine technology. Then, the Y-12 and Foresite team will be in a position to obtain funding from the Department of Defense to further the harder to prove research and development challenges, such as establishing that the Magnofex technology can be effective at tin whisker mitigation.

Foresite’s numerous funded projects in this research and development area and the proven opportunity for success in addressing a number of performance issues in lead free soldered and plated electronic systems enable Y-12 to demonstrate ways to solve the difficult problems that have remained unattainable by other government agencies and industry.